Project Description

Located in Clarington, Ontario, OPG’s Darlington Nuclear station began operating in the early 1990s with major refurbishments beginning in the mid 2010s.  The Darlington Refurbishment Project includes various upgrades to the reactor facilities as well as a wide range of upgrades to site services and ancillary support buildings including decommissioning of some site services.

Sarafinchin Associates Ltd. was retained to provide geotechnical inspection and materials testing services in support of the decommissioning of various facilities including the large Construction Water Storage Tanks (CWSTs), Pump House buildings and other site buildings.

The CWSTs were originally designed as twin 1000 m³ capacity bladder type tanks supported within an earth fill embankment having a height of approximately 4.8 m and side slopes of 1 vertical to 1.5 horizontal.  The decommissioning of the tanks and levelling of the berms would potentially provide up to 17,000 m³ of reusable backfill soil, subject to geotechnical assessment.

Sarafinchin engineering staff carried out an extensive test pit investigation of the CWSTs to evaluate the geotechnical suitability of the existing berm fill soils for potential reuse as backfill for various site excavations.  Bulk soil samples of in situ fill soils as well as select imported aggregates were obtained from the site and delivered to the Sarafinchin materials testing laboratory for grain size testing, Standard Proctor and Modified Proctor maximum dry density determination.  Based on the results, Sarafinchin provided recommendations for reuse of the excavated fill soils as well as fill material compliance with the OPG project specifications.   The field and laboratory evaluation by Sarafinchin Associates Ltd. determined that the majority of the excavated soils on site could be reused where needed. Earthworks compaction control by Sarafinchin confirmed that backfill materials were placed and compacted to a minimum of 95% of the Materials Modified Proctor maximum dry density.